Apparatus for continuous analysis of fluid mixtures



J. ROSENBAUM 2,468,638

APPARATUS FOR CONTINUOUS ANALYSIS OF FLUID MIXTURES Filed Jan. 17, 1945 April 26, 1949.

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ARC CELL mrfwmf/*ER A.c. D x L -lN P SPEC TROPHOTDMETER Puo'rocsu. AMPLIFIER Patented Apr. 26, 1949 APPARATUS FOR CONTINUOUS ANALYSIS OF FLUID MIXTURES Eugene J. Rosenbaum, Lansdowne, Pa., assignor to Sun Oil Company, Philadelphia, Pa., a corporation of New Jersey Application January 17, 1945, Serial No. 573,282

(Cl. Z50-43) 5 Claims.

This invention relates to apparatus for analyzing fluid mixtures and in particular is directed to apparatus for determining the conjugated d1- olein content in a stream of hydrocarbon gases.

The invention is predicated on the use of continuous ultra-violet radiation since it is known that conjugated diolens strongly absorb certain ultra-violet wave-lengths. Optical systems, such for example, as a spectrophotometer, or optical filter colorimeter have heretofore been used with a source of continuous ultra-violet radiation to separate the radiation into its constituent wave-lengths and to transmit rays of desired wave-lengths through a sample which is to be analyzed.

It is the usual procedure to make analyses of this type in the laboratory under such conditions that variations in the intensity of the radiation emitted by the source are not of particular consequence since laboratory analyses are of relatively short duration. However, in making uninterrupted analyses on commercial plant streams over relatively long periods of time, such as, continuous daily analyses, the constancy of the emission of the radiation source is of basic importance because any variation would have the same eiect as a change in the concentration of the component for which the analysis is being made and as the result the analysis would be inaccurate. the previous procedure has been to supply energy to the ultra-violet source by means of an electronic power supply consisting of a vacuum tube, rectifier and an electronic circuit for maintaining a constant direct current. Although the results obtained have been satisfactory, the apparatus required and its upkeep are relatively expensive. In addition, due to the complicated and delicate nature of the equipment an operator must be well versed in electronics to prop- .d

erly take care of the equipment. Prior devices, consequently, have not been entirely successful in meeting commercial demands.

The present invention provides an apparatus which will remain operative over extended periods of time, is rugged in construction, simple in design and inexpensive to produce and maintain in working condition.

In the accompanying diagrammatic representation of the apparatus, X and Y represent the lines for the passage of current, for example, from a 110 A. C. power supply to energize the ultra-violet radiation source C. A constant voltage transformer D has its input inductance coil D1 connected to the supply lines X and Y To achieve the desired constancy and its output inductance coil D2 connected by lines E and F respectively with the anode or plate G and cathode or filament H of the ultraviolet light source C which as designated is of the hydrogen arc type. A variable resistance I is placed in line E in series with the output inductance coil D2 and the plate G to adjust the current to the hydrogen arc C as desired and the ammeter A is provided to indicate the current. The usual storage battery indicated at K is provided for heating the filament H of the hydrogen arc.

The optical system L may comprise a spectrophotometer of the Beckman quartz photoelectric type, described in Journal of the Optical Society of America, vol. 3l, No. 1l, pages 682-689, November 1941, which functions to separate the radiation from the hydrogen arc C into its constituent wave-lengths and to transmit rays of the desired or selected Wave-length through the gaseous mixture which passes continuously through absorption cell M. A photo cell N is arranged to receive the fraction of the selected Wave-length, which is transmitted through the mixture in the absorption cell, in order to measure its intensity. An amplifier O is placed in circuit with the photo cell for amplifying the photo-current produced by the transmitted radiation, and the output of the amplifier is fed to a recording potentiometer P for effecting a record. Since the gas mixture to be analyzed will pass through the absorption cell continuously the recording potentiometer will be of the type adapted for continuous recording.

The details of construction of the spectrophotometer, absorption cell, photo electric cell and the recording potentiometer or the particular manner in which they are assembled for operation are not necessary for an understanding of the invention since these elements are well known and may be purchased as separate units or assembled to eiect the desired results.

The source of ultra-violet light must be continuous, that is, it must contain all Wave-lengths in the ultra-violet range. The most suitable type of lamp is a low voltage hot-cathode hydrogen discharge tube, such for example, as the type described by R. H. Munch in the Journal of the American Chemical Society, vol. 5'7, page 1863, published 1935.

This apparatus is applicable to the analysis of a iiuid mixture for the determination of the concentration of any component contained therein which has an absorption band in the ultra-violet portion of the spectrum. In the operation the spectrophotometer is adjusted to select from the absorption band of the component, the concentration of which is to be determined, a particular wave-length which Will minimize or practically eliminate the interfering influence of the other substances in the fluid mixture. In one commercial application of the apparatus, for example, the spectrophotometer is set at 2,350 Angstrofrn units in order to determine the butadiene concentration in a hydrocarbon stream. The absorption band for butadiene is between 2100 and 2400 Angstrom units and the particular Wave-length of 2350 Angstrom units was selected after determination that it would have appreciable absorption at this Wave-length While at the same time, the interfering influence of other components of the stream, such as, monolefins, was greatly minimized or practically eliminated.

It will of course be understood that the particular component of the fluid stream for Which analysis is being made Will be the chief controlling factor in the selection of the Wave-length for which the optical system is set, while the remaining constituents in the stream may have some minor effect on the selection of the particular wave-length.

What I claim and desire to protect by Letters Patent is:

1. Apparatus for fluid analysis which comprises a source of continuous ultra-violet radiation of substantially constant intensity including cathode and anode electrodes, an absorption cell for containing a sample to be tested, means for impressing a constant alternating voltage across said electrodes, said means including a constant voltage transformer and a variable resistance in series with said anode, an optical system for separating the ultra-violet radiation into its constituent wave-lengths and for transmitting rays of desired Wave-length through said sample, and means for measuring and recording the intensity of radiation emerging from said sample.

2. Apparatus for gas analysis to determine butadiene content which comprises a hydrogen arc having cathode and anode electrodes for producing ultra-violet radiation of substantially constant intensity, an absorption cell for the passage of a continuous gas stream which is being tested, means for impressing a constant alternating Voltage across said electrodes, said means including a constant voltage transformer and a variable resistance in series With said anode, an optical system for separating the ultra-violet radiation into its constituent Wave-lengths and for transmitting rays of wave-length in the range of 2100 55 to 2400 A., and means for measuring and continuously recording the intensity of radiation emerging from said sample.

3. Apparatus for gas analysis to determine conjugated diolen content which comprises a hydrogen arc, means for maintaining the intensity of said hydrogen arc substantially constant, said means including a constant voltage transformer having input and output coils, means for supplying alternating current to said input coil, a variable resistance in series with said output coil and the hydrogen arc, an optical system for separating the ultra-Violet radiation into its constituent Wave-lengths and for transmitting rays of desired Wave-length through said sample, and means for measuring and recording the intensity of radiation emerging from said sample.

4. Apparatus for gas analysis to determine conjugated diolen content which comprises a source of continuous ultra-violet radiation of substantially constant intensity consisting oi a hydrogen arc having cathode and anode electrodes, an absorption cell for containing a sample to be tested, means for impressing a constant alternating voltage across said electrodes, said means including a constant voltage transformer and a variable: resistance in series with said anode, means for heating said cathode to suitable operating temperature, an optical system for separating the ultra-violet radiation into its constituent Wavelengths and for transmitting rays of desired wavelength through said sample, and means for measuring and recording the intensity of radiation emerging from said sample.

5. Apparatus for uninterrupted uid analysis using the ultra-Violet region of the spectrum comprising a substantially constant intensity source of continuous ultraeviolet radiation including a low voltage, hot cathode hydrogen discharge tube consisting of a cathode and an anode, a constant voltage transformer connected across said cathode and anode and a variable resistance between said transformer and the anode; an absorption cell for the continuous passage of a iiuid sample to be analyzed; an optical system for separating the ultra-violet radiation of said source into its constituent wave lengths and for transmitting rays of desired Wave length through the sample in said absorption cell; and means for measuring and recording the intensity of radiation emerging from said sample.

EUGENE J. ROSENBAUM.

REFERENCES CITED The following references are of record in the le of this patent:

UNITED STATESy PATENTS Number Name Date 2,123,573 McFarlan July 12, 1938 2,265,357 Demarest Dec. 9, 1941 2,269,674 Liddel et al Jan. 13, 1942 2,350,001 Van den Akker May 30, 1944 

